Fine Tunes #9

Okay, let's return to the power grid. In the February installment of "Fine Tunes", we learned that typical domestic 110V AC supplies are derived from that 220V transformer out on the pole. The center-tap 110V supply is unbalanced, but if you take 220V service, you're getting balanced power. One thing you can do is take 220V down to 110V with a step-down transformer. George Cardas swears by it. He's also experimenting with a Statpower Technologies Prosine 1000 Full Square Wave Converter hooked to a big mutha battery to power his front-end components.

"Yep, it sounds great! It's enough to keep the system up for around half a day using a fairly serious battery called the Ultima. It huge, puts out a thousand amps, and costs about $150."

The Statpower is available from the West Marine catalog and retails for $699.

When it comes to using step-down transformers, Les Edelberg of Audio Power Industries demurs. Naturally enough, he points to his own line of Power Wedge Ultras as better suited to the task at hand. Filtering and isolation transformers with a center-tapped secondary referenced to ground yield a stable ±60V per side. Since the two legs are 180 degrees out of phase, common-mode noise, which by definition will be the same on each leg, is canceled and you've got a balanced 110V supply. These new Wedges also offer several configurable ground-reference options for best performance.

Of course, the "Fine Tunes" brief is low- or no-cost techniques for improving your system's sound. So let's consider that unruly beast called Ground. Aside from walking on, what's it good for?

First, a few basics. The AC at the wall is polarized. There's hot (supply) and neutral (return), the latter referenced to ground. What is ground? In theory it is the planet Earth, on which we all dwell. But look at it this way: The center tap of the 220V input is "bonded" (by law) to ground at a building's main service input panel. Effectively, the center tap is neutral, and ground and neutral should be at the same potential at that point. But, ah-ha—a few feet away, they begin to diverge. Ground is still ground, neutral still the AC return, but neutral gets pulled away from ground by loads from other household appliances, for example. And there's noise riding on the power line, and even noise generated within your audiophile components, that feeds back through the power cord into the line. (A partial explanation for why power cords, which each have a different filtering action on this noise, sound different?) DVD players and microprocessor-controlled turntables (of all things) are well-known offenders.

And how 'bout that class-AB amp you love so much? On musical peaks it might draw enough current to notch the top and bottom of the AC waveform, or even flatten the dickens out of it, leaving slim pickin's for the rest of the front-end to sup on. Budding electrician though you may be, remember that neutral and ground should never be connected.

Here's a tip. Have you ever been startled by a hum when hooking up a video cable to an audio system? Once again, by law, the cable company has to "bond" to ground at the point of entry. These two grounds are most likely at different potentials—hook 'em together and bzzzzzzzzz. There are products, like Mondial's MAGIC, that are designed to eliminate the ground loop on the cable while keeping the cable's impedance at the required 75 ohms, by the way.

So get you a good ground. If you live in a private home, that could be a composite ground rod driven deep into Mother Earth. In our old loft building—which, I'm grateful, is not coupled to the outside world with plastic plumbing pipes—we use a large-gauge copper wire banded securely to a cold-water pipe and linked directly to the ground connections in our dual-quad hospital-grade receptacles. I use a speaker binding post tied to the copper bus bar to hook component chassis to ground. Very convenient.

There's something else you should know about your AC receptacles. The best ground is achieved by hooking the green ground wires directly to the duplex receptacles they service rather than to the metal wall box. Do this yourself if you're experienced with handling your outlet, ahem, or get an electrician and explain what you want. While you're at it, make sure to use the screw-down connections in the receptacle rather than those flimsy spring-clips. If the electrician deadpans, invite him or her to stay and listen to the system. Even if he doesn't fully appreciate the sound, he'll be stunned by the shit-eating grin you'll be flashing.

Let's now turn our attention to plug orientation. As revealed last month, hot and neutral are connected to a component's power transformer, and some current leakage is common. Usually one orientation of the AC plug causes less leakage than the other, and finding out which is which is relatively easy. First, disconnect all cables from the component; you want to eliminate all other paths to ground. Plug the unit into the wall and grab your trusty RadioShack voltmeter. Touch the negative probe to ground and the hot probe to a chassis screw. A good ground to use might be at the preamp, the hub of your system. Or you can touch the negative probe to the screw securing the faceplate of the outlet into which the unit is plugged.

Check the reading, then reverse the plug's orientation, using a cheater plug if necessary. Whichever AC plug orientation measures the lowest voltage is usually the better sounding. However, using cheater plugs in your system may result in other problems, which I'll go into next month. Once you've done this with all the components in your system, the cumulative effect might surprise you.

If the idea of messing about with a voltmeter turns you off, you can pick up the Elfix polarity tester for something under $30 through most audiophile mail-order houses. It's easy to use, and doesn't require you to actually touch the piece of equipment you're checking. Now get out there and get polarized!

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